The present invention broadly relates to material handling apparatus, and more particularly to a new and improved construction of apparatus for stacking products, especially printed products, and in particular folded printed products.
The stacker apparatus of the present invention is of the type comprising a stacker chute or channel which can be loaded with the printed products from its top end or upper region and at least one pair of press or contact elements arranged at one side of the stack or stacker chute. This pair of press or contact elements can be driven to move to-and-fro in the lengthwise direction of the stack chute and periodically engages into such stack chute, in order to thus press against the momentarily uppermost located printed product of the stack.
One such type of apparatus has been disclosed, for instance, in U.S. Pat. No. 3,231,100, granted Jan. 25, 1966, entitled "Automatic Jogger Mechanism", especially in FIGS. 7 and 8 of such patent. With this prior art apparatus, the press or contact elements, arranged adjacent one another and constructed approximately in the form of an angle element, are synchronouly driven by a crank drive in such a manner that the free ends of one leg of each angle element describes an essentially oval path. Further, during the course of the downward stroke the free end of each such leg of the angle elements engages into the stack chute or channel, and thus, exerts a pressure force upon the edge of the uppermost situated printed product. At the end of the downward stroke, the free ends of such angle elements however depart from the stack chute, in order to carry out an upward movement or stroke externally of such stack chute. This means, however, that with the state-of-the-art apparatus also the pressure or contact action, exerted upon the stack which is in the process of being formed, is periodically interrupted. Particularly when processing stacks formed of comparatively thick, folded printed products such interruption of the pressure force is disadvantageous, because such type stack, especially when reaching a certain height, tends to behave to a certain extent like a spring which elongates as soon as the pressure force is no longer exerted. Such return spring action, with the prior art equipment, if it is charged with folded printed products, can lead to the undesirable result that the entire elevational stroke of the press or contact elements is not sufficient to compensate for the return spring action which arises during the periodic interruption of the pressure or contact force.
By way of completeness, it is here further mentioned that also other apparatuses are known to the art--which only to a certain extent can be compared with the present invention--, wherein there is exerted a pressure force upon the growing stack. Thus, for instance, with the equipment disclosed in either French Pat. No. 2,043,587 or German Pat. No. 1,189,087 there are provided rotating roll brushes which, according to the aforementioned German Pat. 1,189,087, engage at one upper side edge or edge of the printed products, or as disclosed in the aforementioned French Pat. No. 2,043,587, engaged at two oppositely situated upper side edges or edges, and thus, exert a downwardly effective force, without hindering the further loading or charging or the stack. However, the action of these brushes is that the side edges of the printed products, where they engage, are exposed to an erasing or scraping action, so that the danger exists that these edges of the printed products will be damaged, or, in the case of a folded printed product, that the print will be smudged.
According to a further prior art construction as disclosed in French Pat. No. 2,223,287, the stack is charged from below and the top side of the stack is weighted by means of a set of rolls.
Furthermore, holddown constructions which periodically engage at the edge of the uppermost copy or product of the stack, and thus exert a pressure force thereat, are for instance known from French Pat. No. 287,205 and German Pat. No. 1,122,553. Also here, however, the pressure force exerted upon the stack experiences a periodic interruption, resulting in all of the drawbacks which have already been described above in conjunction with the equipment disclosed in the previously mentioned U.S. Pat. No. 3,231,100.